Tens transfer mechanism with provision for end-around carry



-' NOV. 4, 1969 c, G 5 SERRE ET AL TENS TRANSFER MECHANISM WITH PROVISION FOR END-AROUND CARRY Filed Dec.

2 Sheets-Sheet 1 INVENTORS CHARLES C. DE SERRE THOMAS L. JOHNSON M4264 ATTORNEY NOV. 4, 1969 c 5 SERRE ET AL 3,476,920

' TENS TRANSFER MECHANISM WITH PROVISION FOR END-AROUND CARRY Filed Dec. 23, 19% 2 Sheets-Sheet 2 United States Patent 3,476,920 TENS TRANSFER MECHANISM WITH PROVISION FOR END-AROUND CARRY Charles G. De Serre and Thomas L. Johnson, Rochester, Minn., assignors to International Business Machines Corporation, Armonk, N.Y., a corporation of New York Filed Dec. 23, 1966, Ser. No. 604,274 Int. Cl. G06c 15/26 U.S. Cl. 235-137 1 Claim ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION This invention relates to an accumulator tens transfer mechanism having provision for the automatic transfer of an end-around carry, otherwise known to the art as an elusive 1, fugitive 1 or overflow digit.

In the art of mechanical accumulation where the same accumulating mechanism is employed to receive both positive and negative inputs and thus to store both positive and negative balances, no means has yet been devised for simply and economically handling the end-around carry or fugitive 1. The latter are common terms given to the phenomenon occurring in any mechanical add-subtract accumulation system when the stored balance changes polarity, i.e., when an input having a sign opposite to and a magnitude greater than the stored balance is added into the accumulator. The high order digit indicator sets up a carry which must be transferred into the low order digit indicator in order to render the final total mathematically correct.

The solutions presented by the prior art for handling the end-around carry situation universally call for the addition of special mechanism, additional to the mechanism for effecting the transfer of intermediate carries, for sensing the setup of a carry in the high order digit indicator and for adding the carry into the low order digit accumulator at some appropriate subsequent time. Some of these mechanisms even call for manual assistance such as the depression of an add 1 key which is made a mandatory prerequisite to the taking of a total following the cycle in which a high order carry is detected.

OBJECTS AND SUMMARY OF THE INVENTION It is an object of the invention to provide an accumulator wherein a portion of the mechanism employed to effectuate the transfer of intermediate carries is also employed for the transfer of end-around carries.

Another object is to provide an accumulator having an end-around carry mechanism which is extremely simple and low in cost and which eliminates the requirement for additional end-around mechanism which is substantially different from the intermediate carry transfer mechanism.

In accordance with the principles of the invention, an accumulator is provided wherein the intermediate carry transfer mechanism calls for elements which are pivotable about a common shaft. The transfer of endaround carries is eifectuated by rotating this common shaft. Further, the mechanism employed for detecting the occurrence of a 3,476,920 Patented Nov. 4, 1969 high-order carry and for transferring a carry digit into the low order accumulator position in response thereto is identical to the corresponding mechanism employed in the intermediate carry detection and mechanism. As a result, the amount of special hardware required for the effectuation of the end-around carry operation is kept to an absolute minimum with a concomitant savings in hardware and assembly cost. Further, an output signal indicating the occurrence of an end-around carry may be taken simply and directly from the common shaft for use by any appropriate external mechanism.

The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of a preferred embodiment of the invention, as illustrated in the accompanying drawmgs.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective, exploded view of a preferred embodiment of an accumulator constructed in accordance with the principles of the invention.

FIG. 2 is a rear elevation view of the accumulator of FIG. 1.

FIG. 3 is a sectional view taken along the line 3-3 of FIG. 2.

FIG. 4 is a diagram mathematically illustrating the nature of the end-around carry operation.

DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in the exploded view of FIG. 1, the accumulator assembly 18 comprises two main portions, a vertically shiftable frame 30 and a laterally shiftable frame 32 which is supported in the frame 30. The frame 30 comprises a pair of slideplates rigidly spaced apart from one another by support shafts 40, 122 and 124. Journaled for rotation in side plates 120 are shafts 48 and 41. The former of these shafts carries a plurality of trip and transfer wheels such as the wheels 43" and 45. Shaft 41 supports a plurality of carry transfer drive wheels such as the wheel 47". These latter wheels cooperate, as described subsequently, with the transfer wheels 45 to culminate the transfer of carries during the carry transfer portion of the accumulation cycle.

Bars 121 extend from sideplates 120 to enable the frame 30 to shift vertically in a pair of slots provided in the side walls (not shown) of the machine frame. The purpose of vertical shifting of the frame 30 is to enable engagement of the accumulator digit wheels such as the wheels 42 and 44 carried in frame 32'with a set of differential actuators whereby desired input and output operations may be achieved. The apparatus for accomplishing the vertical shifting operation as well as for driving the differential actuators is not herein described since it does not constitute a part of the present invention. However, reference may be had to U.S. Patent No. 3,384,301, entitled Plus and Minus Accumulator filed by J. W. Berkman et al. on even date herewith for a complete description of these ancillary mechanisms.

Lateral shifting frame 32 comprises a pair of sideplates rigidly spaced apart by a bar 136 and a pair of shafts 132 and 134. Frame 32 supports the accumulator digit wheels 42 and 44 on a shaft 34 journaled in sideplates 130. Eah accumulator digit position includes two ten-tooth digit wheels, the plus wheel 42 and the minus wheel 44, interconnected by a face gear 46. The wheels 42 and 44 of each digit position are interconnected via their respective gear 46 in a 9s complement fashion, i.e., when one of the wheels is set to store a 0 the other wheel stores a 9, etc. Each wheel has one wide carry transfer tooth, such as tooth 42a, the purpose of which is explained subsequently. The total number of pairs of complementary digit wheels 42-44 constitutes the maximum digit capacity of the accumulator.

Frame 32 is slidably supported in the frame 30 by shaft 34 which is journaled in the holes 36 of the sideplates 120 and by shaft 40 which runs through holes 38 of sideplates 130. The purpose of lateral shifting of frame 32 is to enable alignment of either the plus wheels 42 or the minus wheels 44 with the common set of differential actuators whereby the desired positive or negative input and output operations may be performed. To add a positive number into the accumulator, the differential actuators operate on the plus wheels 42 and to add a negative numher into the accumulator the differential actuators operate on the minus wheels 44. Further, a positive balance stored in the accumulator is read out of the positive wheels 42 and a negative balance is read out of minus wheels 44. Appropriate mechanism for accomplishing lateral shifting of frame 32 is described in the aforementioned copending patent application.

The end-around carry operation is mathematically illustrated in the example shown in FIG. 4. As there shown, when the balance stored in the accumulator is +124 the plus wheels are set at 124 and the minus wheels are set to 875, which is the 9s complement of 124. To add a 349 to this balance, the differential actuators add 349 into the minus wheels as shown at A. This addition changes the minus wheels to 224 and the plus wheels to the corresponding complement, 775. However, the addition operation also generates a carry out of the high order digit position. This carry must be added in an end-around carry transfer to the low order digit of the minus wheels, as shown at B, in order to achieve the mathematically correct balance of 225. Once this end-around carry has been effected, the minus wheels are set at 225 and the plus wheels at 774.

When a +230 is added to the 225 balance the sign of the balance is again reversed and the result, as shown in C, is to change the plus wheels to 004 and to cause another end-around carry to be generated, this time out of the high order digit position of the plus wheels. As shown at D the transfer of this carry into the low order digit position of the plus wheels achieves the mathematically correct balance of +005 and, of course, sets the minus wheels to the 9s complement 994.

The carry transfer mechanism of the present embodiment is shown in greater detail in FIGS. 2 and 3. The rotatable shaft 48 supports a plurality of pairs of fourtooth trip and transfer wheels 43 and 45. There is one pair of trip and transfer wheels associated with each of the six pairs of digit wheels. Each pair of trip and transfer wheels is operatively associated only with the digit wheel of its respective pair of digit wheels which is aligned with a differential actuator 20. As shown in FIG. 2, the lateral shifting frame is in its left-hand position whereby the plus accumulator wheels 42 are aligned with the actuators and whereby each corresponding pair of trip and transfer wheels is aligned with one of the digit wheels 42. The trip wheel 43 of each set is positioned to cooperate only with the wide tooth of the associated digit wheel. Each transfer wheel 45 is positioned so that its teeth coact with the regular teeth of the digit wheel and with the teeth on the corresponding carry transfer drive wheel 47 Each trip wheel 43 is rigidly connected to rotate with the transfer wheel associated with the next higher order digit position. For example, the trip wheel 43' associated with plus digit wheel 42' is connected by a sleeve 53 to rotate with the transfer wheel 45 associated with the adjacent higher order digit wheel. The assembly consisting of trip wheel 43', sleeve 53 and transfer wheel 45 is freely rotatable about shaft 48. The same is true of the four other similar assemblies. The trip wheel 4 associated with the highest order digit wheel is pinned to shaft 48 as is the transfer wheel 45" associated with the low order digit wheel. This is the means by which end-around carries are transferred out of the high order digit position and into the low order digit position.

Shaft 41 journaled in side plates below the shaft 48, supports a plurality of transfer drive wheels 47. There is one wheel 47 aligned with each transfer wheel 45. The teeth on the wheels 47 are spaced so as to engage the teeth of their respective transfer wheels 45, and thus to transfer carries, serially. A pinion 49 on shaft 41 cooperates with a vertically fixed, horizontally reciprocable rack 51 when the frame 30 is in its lower position. Rack 51 is cam driven at carry transfer time near the end of the accumulation cycle to drive the wheels 47 through one revolution in a clockwise direction (FIG. 3) to transfer the carries which were set up during the preceding add-in portionof the accumulation cycle. After the carry transfer operation has been completed, rack 51 rotates the wheels 47 in a reverse direction back to their home positions.

OPERATION Referring to FIG, 3, operation of the carry transfer mechanism is as follows. During the add-in portion of the accumulation cycle, the digit wheels 42 (assuming a positive add-in operation) are in engagement with the teeth on the differential actuators 20. The actuators are traveling to the right to impart an amount of clockwise rotation to the digit wheels 42 which is proportional to the desired input digits. When the wide tooth 42a as sociated with the highest order digit wheel 42 is rotated past the tooth 43a" of the associated high order trip wheel 43" it causes the trip wheel to rotate approximately 12 degrees counterclockwise. This indicates that the digit wheel 42 has rotated from the 9 position to the 0 position during the input operation and sets up an endaround carry.

Since trip wheel 43" is pinned to shaft 48 as is the transfer wheel 45" associated with the lowest order digit wheel, the transfer wheel 45" is also rotated approximately 12 degrees counterclockwise and the tooth 45a" thereof is interjected into the path of the teeth on the transfer drive wheel 47 (FIG. 2). When drive wheel 47" is rotated clockwise during the carry transfer portion of the accumulation cycle when the transfer drive rack 51 is actuated, transfer wheel 45" is driven approximately 78 counterclockwise and a tooth thereon imparts a single tooth increment of clockwise rotation to the lowest order digit wheel, adding the carry digit thereinto.

It should be understood that an end-around carry can also be set up during the carry transfer operation when the addition of a carry into the high order digit position causes digit wheel 42 to rotate from 9 to 0. This is the reason for the serial transfer operation.

The above-described operation is for an end-around carry. It is to be understood that intermediate carries are transferred in the same manner. The only difference is that each trip wheel 43 rotates the adjacent transfer 45 through a connecting sleeve 53, rather than through a shaft 48. During readout cycles, the tops of the teeth on trip wheels 43 serve as stops to arrest the reverse rotation of the digit wheels in the 0 position.

As illustrated in the drawings, appropriate detent means should be provided on the digit wheels and the trip and transfer wheels to prevent overshooting thereof and to prevent rotation thereof in response to extraneous forces.

It is .to be noted that in an add-only accumulator a variation of the present invention can be employed to generate an overflow signal when the capacity of the accumulator is exceeded. In such a scheme the abovedescribed carry transfer arrangement would be employed without low order transfer wheel 45" (which, of course, has no utility in an add-only accumulator). The overflow signal is taken directly from shaft 48.

While the invention has been particularly shown and described with reference to a preferred embodiment thereof, it will be understood by those skilled in the ant that the foregoing and other changes in form and details may be made therein without departing from the spirit and scope of the invention.

We claim: 1. An accumulator comprising an assembly having a plurality of ordinally arranged pairs of digit wheels mounted about a common axis,

each of said pairs of digit wheels including a plus wheel and a minus wheel interconnected by a crown gear for mutual counter rotation to effect storage in 9s complement fashion,

each of said digit wheels including a carr transfer tooth, and

said assembly being selectively shiftable to bring all digit wheels of a common sign into a sequence of aligned locations;

a series of toothed carry drive wheels each including a plurality of angularly spaced teeth to effect primary and secondary serial transfers during a single rotation of said carry drive wheels;

a rotatable shaft;

an intermediate order trip gear mounted to rotate unidirectionally about said shaft and positioned in alignment with the carry transfer tooth on an intermediate order aligned digit wheel to effect angular displacement of said trip gear by said carry transfer tooth when said digit wheel rotates from 9 to 0;

a transfer gear mounted to rotate about said shaft in unison with said trip gear, said transfer gear being in alignment and engageable with a carry drive wheel and with the aligned digit wheel which is next higher in order with respect to said intermediate order digit wheel, whereby said angular displacement of said trip gear causes a tooth of said transfer gear to be interjected into the path of the teeth on said carry drive wheel, conditioning said transfer gear to be further displaced by rotation of said carry drive wheel to transfer a carry to said next higher order digit wheel;

a second trip gear connected to said shaft and adapted to rotate the latter, said second trip gear being positioned in alignment with the carry transfer tooth on the highest order aligned digit wheel, whereby said carry transfer tooth angularly displaces said second trip gear and said shaft when said aligned highest order digit wheel rotates from 9 to 0; and

a second transfer gear mounted to rotate with said shaft and positioned in alignment with a second carry drive wheel and with the lowest order aligned digit wheel, whereby said angular displacement of said shaft causes a tooth of said second transfer gear to be interjected into the path of the teeth on said second carry drive wheel, conditioning said second transfer gear to be further displaced by rotation of ,said carry drive wheel to transfer a carry to said lowest order digit wheel.

References Cited UNITED STATES PATENTS 981,633 1/1911 Fuller 235-9 2,838,241 6/1958 Philipp 235138 3,102,688 9/1963 Gang 235137 STEPHEN I. TOMSKY, Primary Examiner US. Cl. X.R. 235l 

